Hi, I work with Paul and I've been investigating this issue.  I created
a program for analyzing the leases file.  It reads the IA-NA and
addresses from the lease and performs the hashing function to find how
many iterations the given address took to generate.

For a leases file from one of our servers, 25,557 of the 79,003 leases
took more than one iteration.  The total number of addresses generated
is 162,112, over double the number of actual leases.  For comparison, I
used dibbler to load one of our test servers with 398,886 leases and
only 19 required two generations.

One difference from my test case is that both of our real servers send
offers but only one of them is receiving a reply (they serve the
same /64s with addresses from independent /96s).  Is it possible that
the servers are skipping addresses because they've already offered them
and somehow they are not expiring correctly?